Metal detectors which can be used to locate metal articles which can be concealed in walls, in particular, are known. An alternating magnetic field is usually generated by means of a transmission coil in a metal detector of this kind. A pair of reception coils which are connected electrically in series and are oriented back-to-back in parallel is arranged in the region of the generated magnetic field. If there is no metal article in the region of the coils, voltages which are induced in the two reception coils have opposite signs and are cancelled out by the series connection. If a metal article in the magnetic field is at unequal distances from the two reception coils, unequal voltages are induced in the reception coils, with the result that a reception voltage of the reception coils which are connected electrically in series is not equal to zero. The reception voltage is amplified by means of an amplifier and then compared with a threshold value. If the reception voltage exceeds the threshold value, a signal which indicates the metal article is output.
In order to be able to sense a small metal article and/or a metal article which is far away from the coils, the magnetic field which is generated by the transmission coil can be strong and an amplification factor of the amplifier can be large. However, a large metal article and/or a metal article which is close to the coils can in this case lead to a reception voltage which overcontrols the amplifier. Exact determination of the location and/or the borders of the metal article can be adversely affected by such a great sensitivity of the metal detector. The prior art discloses metal detectors of which the sensitivity can be manually adjusted by a user. Furthermore, DE 10 2005 007 803 A1 discloses a metal detector in which different sensitivities are realized by changing a frequency of the alternating voltage across the transmission coil.
However, frequency adjustment of this kind requires complex circuitry and, in the case of implementation by means of a programmable microcomputer, may require a relatively powerful processing unit. Manufacturing costs of the metal detector may be increased in both variants.
The disclosure is based on the object of specifying a measuring apparatus for sensing a metal article, a method for sensing the metal article, and a computer program product for carrying out the method, in which measuring apparatus, method and computer program product the sensitivity of the sensing operation can be adjusted in a simple manner.
The disclosure solves these problems by means of an apparatus, a method, and a computer program product, as described herein.